Lungs in situ

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What does it mean in situ? If we were to remove the anterior wall of the thorax without removing or altering any of the structures beneath it, we would see the lungs in their original place, or in situ. Examining the lungs in situ allows us to appreciate their normal anatomy, topography and relations with other structures of the thorax.

Being located into the pleural cavities, the lungs are related with the mediastinum, diaphragm and bones of the thoracic cage. Hence, each lung has a mediastinal, diaphragmatic and costal surface. Note that the lungs don’t occupy the pleural cavities entirely. Thus, inferiorly and anteriorly there are two potential spaces called pleural recesses to which the pulmonary tissue does not extend (or extends only during a forced inspiration), called the costodiaphragmatic and costomediastinal recesses respectively.

Each lung has an apex and a base, as well as the anterior, posterior and inferior borders. The apices of the lungs project into the thoracic inlet, while the bases rest on their respective hemidiaphragms. Although paired organs, the left and right lungs differ anatomically. The left lung has only two lobes (superior and inferior) separated by the oblique fissure. The right lung has three lobes (superior, middle and inferior), separated by the oblique and horizontal fissures.

The following video tutorial will provide you with a detailed overview of the location, anatomical features and relations of the lungs.

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